In the knitting of one-piece panty hose it is known to form the waist opening during the knitting operation as described, for example, in U.S. Pat. No. 3,673,821 to Johnson. The waist opening is defined by a cut or slit extending wale-wise along the knitted fabric, that is in the direction of knitting. Considerable difficulty has been realized, however, because of the tendency of the yarn adjacent the edge of such a longitudinal slit to ravel or breakdown.